Origin and Evolution of Life and Introduction to Classification
Telangana Open School (TOSS) · Class 12 · Biology
Complete topic list for Origin and Evolution of Life and Introduction to Classification in Telangana Open School (TOSS) Class 12 Biology. Key concepts, sub-topics, and what to focus on for board exams.
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Topics in Origin and Evolution of Life and Introduction to Classification
Origin of Life
- Earth formed about 5 billion years ago and was initially very hot with no life.
- Early atmosphere had methane (CH₄), ammonia (NH₃), hydrogen (H₂), and water vapour (H₂O), but no free oxygen.
- Life originated through chemical evolution in water bodies, forming organic molecules from inorganic substances.
Evidence for Organic Evolution
- Organic evolution refers to gradual changes in organisms over generations leading to new species.
- Fossils provide direct evidence of past life forms and transitional stages.
- Embryological similarities among vertebrates suggest common ancestry.
Theories of Evolution
- Darwin proposed natural selection as the mechanism of evolution.
- Organisms produce more offspring than the environment can support, leading to struggle for existence.
- Individuals with favorable variations survive and reproduce — 'survival of the fittest'.
Speciation and Reproductive Isolation
- Speciation is the formation of new and distinct species from existing ones.
- Allopatric speciation occurs due to geographical isolation.
- Sympatric speciation occurs without geographical separation.
Key Concepts
Central concept: Evolution and Classification of Life
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